Decreasing the quantity of carbon dioxide released into earth's atmosphere by industrial processes is a technical challenge of enormous environmental and economic significance. To be able to achieve significant decreases in atmospheric carbon dioxide production without consequently diminishing industrial output and economic activity would be highly beneficial.
One possible approach to achieving these goals is through the electrochemical reduction of carbon dioxide produced by combustion reactions. Because such an approach produces reduced carbon, this can have the additional benefit of generating useable fuels from what had previously been a greenhouse gas emission. For example, electrochemical reduction of carbon dioxide in an aqueous environment can, under the right conditions, produce a mixture of carbon monoxide and hydrogen gas known as syngas. Such synthetic gas can then be processed by known methods into a variety of useable fuels.
Several metals have been tested as possible electrocatalysts for electrochemical reduction of carbon dioxide. Gold can deliver an appreciable current density and reduce carbon dioxide to carbon monoxide with high selectivity at relatively low potential. But gold is not favorable for large-scale applications due to its low abundance and high cost. Copper exhibits a poor selectivity for carbon monoxide production and requires a greater potential to achieve a current density comparable to that achieved by gold.
Silver-based electrocatalysts can selectively promote the reduction of carbon dioxide to carbon monoxide and are considerably less expensive than gold. However, the common polycrystalline silver electrodes that have been employed require a large overpotential for carbon dioxide reduction and show poor carbon monoxide selectivity at low overpotentials, making silver a presently impractical option as an electrocatalyst for carbon dioxide reduction. Systems and methods which improved silver's efficiency and selectivity as a catalyst for electrochemical reduction of carbon dioxide to carbon monoxide would be beneficial.